A 3D electronic module comprises a stack of electronic dies, which are interconnected in three dimensions using the faces of the stack to make the connections between the dies. A die 50, an example of which is shown in FIG. 1, generally comprises one or more active or passive components 11 which have electrical connection elements 2, the components being encapsulated in an electrically insulating resin 6. The connection elements 2 of the components are connected to connection pads 2′ on an electrically insulating substrate 4. One or more electrically conducting tracks 3 on the insulating substrate 4 connect these components together or connect them to elements for electrically connecting the dies together. The dies are electrically connected together via conductors located on the lateral faces of the stack, that is to say on the edges 7 of the dies.
Several methods exist for connecting the pads 2 of the component to the pads 2′ of the substrate.
One method consists in connecting the pads of the component directly to those of the insulating substrate by sending ultrasound waves. The energy sent is proportional to the number of pads to be connected. For components having a large number of pads, the energy needed for the connection sometimes causes the component to break. One solution for reducing this energy consists in heating the substrate, which then softens and adsorbs some of the ultrasonic energy sent, thereby making the connection very difficult. Furthermore, during encapsulation of the components, by curing carried out at about 150° C., the substrate tends to become curved since the expansion coefficient of the components is different from that of the substrate, typically four times smaller.
The dies thus obtained are electrically tested one by one so as to remove the dies having a defective component before they are stacked, in order to obtain a 3D electronic module.